How to fix and reshape messed up shapes in sculpt mode
What exactly are you trying to fix with the hands? From what I understand after reading your question, I assume you want to fix the right hand of the fetus since there are only four fingers, right?

If the fingers were the problem then I would go ahead and delete them. I would then create new geometry to fill up the holes where there used to be the fingers ( using the boolean operator Union to join the new geometry to the fetus's hand). After that, I would use the "snake hook" brush to pull out new fingers (enable Dyntopo when doing this step so that the brush can pull out enough geometries to form new fingers).